Self aligned replacement metal source/drain finfet

ABSTRACT

A fin-shaped field effect transistor (finFET) device comprising includes a substrate. an insulating layer displaced over the substrate, and a fin. The device also includes a gate formed over the fin, the gate including: a gate stack; and a high-k dielectric on opposing side of the gate stack. The device further includes metallic source and drain regions formed over the fin and on opposing sides of the gate.

DOMESTIC PRIORITY

This application is a continuation of U.S. application Ser. No.16/459,685, filed Jul. 2, 2019, which is a continuation of U.S.application Ser. No. 15/136,238, filed Apr. 22, 2016, now U.S. Pat. No.10,418,450, which is a divisional of U.S. application Ser. No.14/943,652, filed Nov. 17, 2015, now U.S. Pat. No. 9,466,693, the entirecontents of each are incorporated herein by reference.

BACKGROUND

The present invention relates generally to semiconductor deviceprocessing techniques and, more particularly, to a method of areplacement metal source/drain fin-shaped field effect transistor(finFET).

The escalating demands for high density and performance associated withultra large scale integrated (VLSI) circuit devices have requiredcertain design features, such as shrinking gate lengths, highreliability and increased manufacturing throughput. The continuedreduction of design features has challenged the limitations ofconventional fabrication techniques.

SUMMARY

In one embodiment, a method of a fin-shaped field effect transistor(finFET) device is disclosed. The method includes: forming at least onefin that extends in a first direction; covering the fin with a dummygate stack that extends in a second direction perpendicular to the firstdirection and that divides the at least one fin into source and drainregions on opposing sides of the replacement gate stack; covering thesource and drain regions with an interlayer dielectric; replacing thedummy gate stack with a replacement metal gate stack; performing a firstanneal at a first temperature after the replacement metal gate stack hasreplaced the dummy gate stack. In this method, after performing thefirst anneal the method further includes: recessing a top portion of theinterlayer dielectric; and forming metallic source and drain regions.

In another embodiment, a fin-shaped field effect transistor (finFET)device is disclosed. The device of this embodiment includes a substrate,an insulating layer displaced over the substrate, a fin, and a gateformed over the fin. The gate includes gate includes a gate stack and ahigh-k dielectric on opposing side of the gate stack. The device alsoincludes metallic source and drain regions formed over the fin and onopposing sides of the gate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Referring to the exemplary drawings wherein like elements are numberedalike in the several Figures:

FIG. 1A shows a perspective view of an example of a finFET device;

FIG. 1B shows a top view of an example of a finFET device;

FIGS. 2A-2C shows a second stage of forming a finFET device;

FIGS. 3A-3C shows a third stage of forming a finFET device and includesa step related to the formation of a replacement metal gate (RMG)process;

FIGS. 4A-4C shows a fourth stage of forming a finFET device and includesa step related to the formation of a replacement metal gate (RMG)process;

FIGS. 5A-5C shows a fifth stage of forming a finFET device and includesa step related to the formation of a replacement metal gate (RMG)process;

FIGS. 6A-6C shows a sixth stage of forming a finFET device and includesa step related to the formation of a replacement metal gate (RMG)process;

FIG. 7 shows a top view after the stage of FIGS. 6A-6C have beencompleted and openings have been formed over the source/drain regions ofthe fins;

FIGS. 8A-8C shows a first stage of forming metal contacts over thesource/drain regions;

FIGS. 9A-9C shows a second stage of forming metal contacts over thesource/drain regions;

FIGS. 10A-10C shows a third stage of forming metal contacts over thesource/drain regions; and

FIGS. 11A-11C shows a fourth stage of forming metal contacts over thesource/drain regions.

DETAILED DESCRIPTION

When the gate length of conventional planar metal oxide semiconductorfield effect transistors (MOSFETs) is scaled below 100 nm, problemsassociated with short channel effects (e.g., excessive leakage betweenthe source and drain regions) become increasingly difficult to overcome.In addition, mobility degradation and a number of process issues alsomake it difficult to scale conventional MOSFETs to include increasinglysmaller device features. New device structures are therefore beingexplored to improve FET performance and allow further device scaling.

Multi-Gate MOSFETs (MuGFETs) represent one type of structure that hasbeen considered as a candidate for succeeding existing planar MOSFETs.In MuGFETs, two or more gates may be used to control short channeleffects. A FinFET is a recent MuGFET structure that exhibits good shortchannel behavior, and includes a channel formed in a vertical fin. ThefinFET structure may be fabricated using layout and process techniquessimilar to those used for conventional planar MOSFETs. The FinFET deviceoften includes active source and drain regions and a channel region thatare formed from a silicon fin. The channel region is wrapped with gatematerials such as polysilicon, metal materials, or high-k materials.

FIGS. 1A and 1B illustrate, respectively, perspective and top views ofan exemplary arrangement of FinFET devices 102. As shown, a deviceincluding three individual FinFETs 105 is illustrated in FIG. 1A andFIG. 1B shows only a single FinFET 105. It shall be understood that aFinFET device having any number of individual FinFET may be formedaccording to the teachings herein. As illustrated, there are no contactsyet formed on the source and drain.

The FinFET device 102 has individual FinFets 105 that include finportions 104 that are arranged in parallel and passing through andisolation layer 101 of a substrate 100. The isolation layer 101 may be ashallow trench isolation (STI) layer in one embodiment. In oneembodiment, the substrate 101 is a bulk substrate and the fin portions104 are contiguous with and formed of the same material as the substrate101.

A gate stack portion 106 is disposed over portions of the fin portions104. In particular, the fins are shown as having source sides 104 a anddrain sides 104 b. The gate 106 is formed, generally over middle thefins. Application of a voltage to the gate will allow a current to passfrom the source side 104 a to the drain side 104 b (or vice versa).

In some cases it may be beneficial to form metallic source/draincontacts on the source and drain sides 104 a, 104 b. Such processing maybe referred to as metallic source drain (MSD) processing herein. Herein,MSD processing is performed after a replacement metal gate (RMG)processing. The inventors hereof have discovered that such ordering maybe required because the RMG process requires a thermal anneal step whichis beyond the thermal stability of the silicides which would act as themain candidates for MSD (NiSi, ErSi, PtSi, etc.). In one embodiment, theorder of processing may also allow for invoking a gate recess in a MSDdevice. Such a recess may improve bulk FinFET delay and short channeleffects.

The following description will define a process flow by which a FinFETmay be formed. In FIG. 1B, four different section lines are shown. Inthe following figures, those labelled with an “A” are a cross-sectiontaken along line A-A or A′-A′, those labelled with a “B” are across-section taken along B-B and those labelled with a “C” are across-section taken along C-C.

FIGS. 2A-2C shows a first step according to one embodiment and FIG. 2Ais taken along line A-A. The device includes a substrate layer 103 withan insulating layer 101 disposed over or directly on it. Herein, theterm “over” shall refer to a layer that is disposed further from asubstrate layer 103 than another layer (i.e., it if further from thebulk substrate in the “x” direction as labelled in FIG. 2A). Thesubstrate layer 103 includes a fin 105 is formed such that it extendsupwardly from the substrate layer 101. The fin 105 and the substrate 103are formed of the same material in one embodiment. In one embodiment,both the fin 105 and the substrate 103 are formed of a bulk substratematerial (e.g., silicon). In practice, the fins may be formed on thesubstrate layer 103 by etching them out of the substrate layer 103, andthen the insulating layer 101 is formed by filling the space between thefins with insulating material, planarizing this material, and thenetching this material to reveal a top portion of the fins.

In another embodiment, the substrate layer may be an SOI substrate. Insuch a case, an insulating layer 101 is formed on top of the SOIsubstrate (in such a case the insulating layer is called a buried oxide,or BOX, layer) and then another SOI layer is formed over the box layerand the fins are etched out of this “top” SOI layer.

The following description related to FIGS. 3-6 generally describes whatis known RMG processing. Certain steps will be generally described butit shall be appreciated that as disclosed herein, performing such RMGprocessing before forming metallic source/drain contacts may providecertain advantages as described above.

FIGS. 3A-3C shows a next step according to one embodiment and FIG. 3A istaken along line A-A. A dummy gate dielectric 302 may be a deposited orgrown oxide layer. The dummy gate dielectric 302 and the insulator 101are then covered by a dummy gate stack material 304 such as an amorphoussilicon. That layer is then covered by a dummy gate cap 306 that may beformed of one or a combination of silicon dioxide, silicon nitride, oramorphous carbon. A pattern may then be etched on the upper surface ofthe gate cap layer 306 and then a chemical or other process may form adummy gate stack 312 on to which sidewall spacers may be formed.Formation of the sidewall spacers 310 is within the knowledge of theskilled practitioner. At the end of the processing described in relationto FIGS. 3A-3C a dummy gate stack 312 sandwiched by spacers 310 has beencompleted. The gate stack 312 is formed as a 3-D element disposedperpendicular to the fin 105 and passes over a top 314 of the fin 105.

FIGS. 4A-4C shows a next processing step and FIG. 4A is taken along lineA-A. In this step, an interlayer dielectric (ILD) 401 is deposited overthe entire structure of the FIGS. 3A-3C. Typically, the source and drainregions are doped either before or when the ILD layer 401 is deposited.The ILD layer 401 will serve to cover the source and drain 104 a, 104 bregions of the fin 104 while the dummy gate 312 is replaced with theactual gate. In FIGS. 4A-4C, the ILD layer 401 is level with a top 402of the dummy gate cap 306.

FIGS. 5A-5C shows the structure after a portion the dummy gate stack hasbeen removed. FIG. 5A is taken along line A-A.

In particular, the dummy gate stack has been removed such that originalfin 105 is shown has been uncovered (e.g, the dummy gate dielectric 302and the dummy gate stack material have been removed in a region betweenthe spacers 310. This may be accomplished in known manners. In oneembodiment, the insulator 101 may optionally be removed in a regionbetween the spacers 310 by a gate recess depth shown at depth D. Therecess may reduce delay and short channel effects.

FIGS. 6A-6C shows the finalized gate formed by a RMG processes. Inparticular, in the region between the spacers 310 has a thin inner layerdielectric layer 602 deposited over the fin 105. Then a high-kdielectric 604 is deposited on or over the thin inner layer dielectriclayer 602. This structure is then completed by the addition of gatestack layer 606 and a cap layer 608. The replacement gate stack layer606 may be formed of one or a combination of workfunction metals(including but not limited to TiN, TiAl, TaN, TiAlC) and a lowresistance metal fill (including but not limited to aluminum ortungsten), while the cap layer 608 may comprise one or a combination ofsilicon dioxide or silicon nitride. Of course, one or more hightemperature annealing steps may have also been performed. As discussedabove, these anneals may be performed at a temperature that destroys orreduces the effectiveness of metal sources/drains. As such, if themetallic drain/source connections were formed before the RMG processing,the device may not be effective. In FIGS. 6A and 6C it can be seen thatthe high-k dielectric 604 is formed on opposing sides of the gate stack606. Such a configuration is typically only found in gates formed by anRMG process.

FIG. 7 shows a top view of device shown in FIG. 1 after the processingof of FIGS. 6A-6C. In this view, the entire device has been covered by amask layer 700 with exposed source and drain 702, 704 regions. That is,the source and drain (104 a, 104 b) are exposed and the gate stack andother regions are covered.

FIGS. 8A-8C shows a next processing step and FIG. 8A is taken along lineA-A. In this step, the ILD 401 in a region outside of the spacers 310 isremoved to a level slightly below an upper surface (top) 314 of the fin105.

FIGS. 9A-9C shows processing after a fin recess 900 is formed in the fin105. The depth of the fin recess is shown as R_(fin) with the upperbound being defined as the upper surface 314 (represented by dashed line902). FIG. 9A and all remaining figures with an A suffix are taken alongsection lines A′-A′ from FIG. 1B.

FIGS. 10A-10C shows the structure after the source/drain have beendoped. In one embodiment, a silicide layer 1002 is formed over the finin the open regions. The layer may be formed with nickel-based materialbeing first deposited over the fin 105 and other exposed regions. Othermaterials may be used to form the silicide layer, such as platinum,erbium, etc. A dopant (shown as region 1004) may then be introduced intothe nickel on the top and sides of the fin 105 and annealed. This annealcauses the metal to become the silicide layer 1002 and the dopant tomove into the fin 105. Another option is to first dope the fin and thenanneal. Then the nickel or other metal is placed and another annealoccurs that results in the formation of the silicide layer 1002 and thedopant region 1004. It shall be noted that the anneals used to form thesilicide layer 1002/dopant regions 1004 are much lower than used in theRMG process and do not harm the gate stack. Yet another option is toutilize a so-called implant into silicide (ITS). In such a process, theimplant takes place after the silicide has been formed.

Lastly, the some or all of the open regions 702/704 are filled with ametal source/drain fill material 1102 as shown in FIGS. 11A-11C. Themetal source/drain fill material 1102 may be any suitable material suchas Al, W, Cu, etc.

While the invention has been described with reference to a preferredembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe appended claims.

What is claimed is:
 1. A fin-shaped field effect transistor (finFET)device comprising: a fin extending horizontally in a first direction,the fin having a channel region with a source region and a drain regionon opposing sides of the channel region, wherein a top surface of thefin in the source and drain regions is lower than a top surface of thefin in the channel region; a gate structure disposed over the channelregion of the fin, the gate structure comprising two opposing sidewallspacers and extending horizontally in a second direction, the seconddirection substantially orthogonal to the first direction; and sourceand drain metal fill regions comprising upper source and drain metalfill regions adjacent the sidewall spacers of the gate structure andhaving a width in the second direction greater than the width of the finin the channel region, and lower source and drain metal fill regionshaving a width in the second direction substantially the same as thewidth of the fin in the channel region.
 2. The finFET device of claim 1,further comprising: a source-side silicide region having a first portionbetween the channel region and the source metal fill region and adrain-side silicide region having a first portion between the channelregion and the drain metal fill region.
 3. The finFET device of claim 2,wherein, the source-side silicide region further comprises a secondportion between the top surface of the fin in the source region and thesource metal fill region, and the drain-side silicide region furthercomprises a second portion between the top surface of the fin in thedrain region and the drain metal fill region.
 4. The finFET device ofclaim 3, wherein the first and second portions of the source-sidesilicide region are contiguous and the first and second portions of thedrain-side silicide region are contiguous.
 5. The finFET device of claim2, wherein the source-side and drain-side silicide regions at leastpartially underlie the outer edges of the opposing sidewall spacers. 6.The finFET device of claim 1, wherein the upper source and drain metalfill regions are disposed in recesses within an interlevel dielectricadjacent the gate structure, and wherein the lower source and drainmetal fill regions overlie the source and drain regions of the fin andare at least partially bounded by the interlevel dielectric on opposingsides in the second direction.
 7. The finFET device of claim 2, whereinthe silicide regions comprise nickel, platinum, or erbium.
 8. The finFETdevice of claim 1, wherein the source and drain metal fill regionscomprise tungsten, aluminum, or copper.
 9. A field effect transistordevice comprising: a fin extending horizontally in a first direction,the fin having a channel region; a gate structure extending horizontallyin a second direction substantially orthogonal to the first direction,disposed upon and covering the channel region; source and drain metalfill regions on opposite sides of the gate structure, at least a portionof each source and drain metal fill region self-aligned in the firstdirection to the channel region of the fin; a source-side silicideregion between the channel region and the source metal fill region; anda drain-side silicide region between the channel region and the drainmetal fill region.
 10. The field effect transistor device of claim 9,wherein the self-aligned portions of the source and drain metal fillregions have substantially the same width as the channel region of thefin.
 11. The field effect transistor device of claim 9, wherein the gatestructure comprises two opposing sidewall spacers, and wherein thesource and drain metal fill regions comprise upper and lower portions,the upper portions adjacent the sidewall spacers of the gate structureand having a width in the second direction greater than the width of thefin in the channel region, the lower portions self-aligned in the firstdirection to the channel region of the fin and having a width in thesecond direction substantially the same as the width of the fin in thechannel region, and wherein the lower portion of the source metal fillregion is in contact with the source-side silicide region and the lowerportion of the drain metal fill region is in contact with the drain-sidesilicide region.
 12. The field effect transistor device of claim 9,wherein source and drain metal fill regions are disposed in recesseswithin an interlevel dielectric adjacent the gate structure.
 13. Thefield effect transistor device of claim 9, wherein the silicide regionscomprise nickel, platinum, or erbium.
 14. The field effect transistordevice of claim 9, wherein the source and drain metal fill regionscomprise tungsten, aluminum, or copper.
 15. A field effect transistordevice comprising: a fin extending horizontally in a first direction; agate structure extending horizontally in a second direction, the seconddirection substantially orthogonal to the first direction, disposed uponand covering first and second sidewalls of the fin; a source-sidesilicide region contacting a third sidewall of the fin, the thirdsidewall extending between the first and second sidewalls, wherein thegate structure overlies the third sidewall; a drain-side silicide regioncontacting a fourth sidewall of the fin, the fourth sidewall extendingbetween the first and second sidewalls, the drain-side silicide regionon the opposite side of the gate structure from the source-side silicideregion, wherein the gate structure overlies the fourth sidewall; andsource and drain metal fill regions on opposite sides of the gatestructure, contacting the source-side and drain-side silicide regions,respectively.
 16. The field effect transistor device of claim 15,wherein each of the source and drain metal fill regions further comprisea lower portion self-aligned to the fin in the first direction.
 17. Thefield effect transistor device of claim 16, wherein the fin comprises achannel region and wherein the self-aligned portions of the source anddrain metal fill regions have substantially the same width as thechannel region of the fin.
 18. The field effect transistor device ofclaim 15, wherein the gate structure comprises two opposing sidewallspacers, and wherein the source-side and drain-side silicide regions atleast partially underlie the outer edges of the opposing sidewallspacers.
 19. The field effect transistor device of claim 15, wherein thefin comprises a channel region, wherein the gate structure comprises twoopposing sidewall spacers, and wherein the source and drain metal fillregions comprise upper and lower portions, the upper portions adjacentthe sidewall spacers of the gate structure and having a width in thesecond direction greater than the width of the fin, the lower portionsself-aligned in the first direction to the channel region of the fin andhaving a width in the second direction substantially the same as thewidth of the fin in the channel region.
 20. The field effect transistordevice of claim 19, wherein the source and drain metal fill regions aredisposed in recesses within an interlevel dielectric adjacent the gatestructure.